1. The document summarizes the metabolism of cholesterol in the body. Cholesterol serves several important functions including as a structural component of cell membranes and as a precursor for the synthesis of bile salts, steroid hormones, and vitamin D. 2. Bile salts are synthesized from cholesterol in the liver through a series of reactions. They help in the digestion and absorption of lipids as emulsifying agents. 3. Cholesterol is also the precursor for the synthesis of steroid hormones including glucocorticoids, mineralocorticoids, progestins, androgens, and estrogens. 4. Vitamin D is synthesized from 7-dehydrocholesterol, an intermediate in cholesterol synthesis, when it

1. BIOCHEMISTRY
[B. Pharm – I Yr.]
Topic: Metabolism of Cholesterol
Umesh Kumar
Assistant Professor
Dept. of Pharm. Chemistry
Hygia Institute of Pharmaceutical Education and Research

2. CONTENTS
• Cholesterol
• Introduction
• Functions
• Synthesis of
-Bile Salt
-Steroid Hormones
-Vitamin D

3. Cholesterol
• Cholesterol is found exclusively in animals, hence it is often called as animal sterol.
• The total body content of cholesterol in an adult man weighing 70 kg is about 140 g i.e., around 2
g/kg body weight.
• Cholesterol is amphipathic in nature, since it possesses both hydrophilic and hydrophobic regions in
the structure.

4. Functions of Cholesterol
• Cholesterol is essential to life, as it performs a number of important functions
1. It is a structural component of cell membrane.
2. Cholesterol is the precursor [or the synthesis of all other steroids in the body. These include steroid
hormones, vitamin D and bile acids.
3. It is an essential ingredient in the structure of lipoproteins in which form the lipids in the body are
transported.
4. Fatty acids are transported to liver as cholesteryl esters for oxidation.

5. Synthesis of Bile Salts
• The bile acids possess 24 carbon atoms, 2 or 3 hydroxyl groups in the steroid nucleus and a side chain
ending in carboxyl group.
• The bile acids are amphipathic in nature since they possess both polar and non-polar groups.
• They serve as emulsifying agents in the intestine and actively participate in the digestion and
absorption of lipids.
• The synthesis of primary bile acids takes place in the liver and involves a series of reactions.
• The step catalyzed by 7 a-hydroxylase is inhibited by bile acids and this is the rate Limiting reaction.
• Cholic acid and chenodeoxycholic acid are the primary bile acids and the former is found in the
largest amount in bile.
• On conjugation with glycine or taurine, conjugated bile acids (glycocholic acid, taurocholic acid etc.)
are formed which are more efficient in their function as surfactants.
• In the bile, the conjugated bile acids exist as sodium and potassium salts which are known as bile
salts.

6. Contin……….

7. Synthesis of Steroid Hormones from Cholesterol
• Cholesterol is the precursor for the synthesis of all the five classes of steroid hormones
(a) Glucocorticoids (cortisol)
(b) Mineralocorticoids (aldosterone)
(c) Progestins (progesterone)
(d) Androgens (testosterone)
(e) Estrogens (estradiol)

9. Contin……….

10. Synthesis of Vitamin D
• 7-Dehydrocholesterol, an intermediate in the synthesis of cholesterol, is converted to cholecalciferol
(vitamin D3) by ultraviolet rays in the skin.

11. THANK YOU
HYGIA GROUP OF INSTITUTIONS
GHAILA ROAD, GAAZIPUR BALRAM,
FAIZULLAHGANJ, LUCKNOW